1. Field of the Invention
This invention relates to a hydraulic adjustable vibration damper with a work cylinder, a piston fastened to a piston rod and dividing the work cylinder into two work chambers, at least one additional tube coaxially surrounding the work cylinder and at least one controllable damping valve installed in a stationary and sealed manner on the side of the vibration damper.
2. Background Information
Hydraulic adjustable vibration dampers that may be known include the vibration damper described in U.S. Pat. No. 4,650,042, entitled Hydraulic Adjustable Shock Absorber, which corresponds to Federal Republic of Germany Patent No. 34 34 877, in which the work piston fastened to a piston rod divides the work cylinder into two work chambers, and in which there is at least one controllable damping valve located laterally on the vibration damper. To form a bypass and for the flow past the controllable damping valve, there is an additional tube outside the work cylinder but inside the jacket tube forming the equalization cheer. The mechanical and electrical parts of the controllable damping valve are held in a base welded onto the jacket tube. Such a lateral welded connection of the base is problematic not only from the fabrication point of view in that it may result in delays, but also in that it is expensive.
Vibration dampers for motor vehicles may be known (e.g. Federal Republic of Germany Patent No. 39 39 012) in which the work cylinder is coaxially surrounded by at least one additional chamber, and in which the inside and outside walls of at least one chamber are formed as a single piece and are connected to one another by means of webs running axially.
The chamber located between the inside and outside wall is divided in the longitudinal direction so that at least two separate chambers are formed, and so that outside, on the outside wall, there is at least one flat area. This flat area for a possible valve connection extends over the entire length of the tube, so that parts surrounding the tube, such as collars, spring plates, brackets, etc. must be provided with a corresponding inner contour, or the flat area must be machined by cutting in the vicinity of collars or brackets, so that the tube retains a cylindrical contour.